Why won't Cortana play certain Songs - Win 10?

I'm using Cortana to play my music. While this is a great feature, it won't play certain songs. Some songs come right up and play, others do not and Cortana gives the response that something went wrong and to try again later. I have the Groove Music player set as default and all of my music was imported into it. If I go into the player and click the songs, they play just fine. Not sure why Cortana is having a problem playing them .